Method for detecting the amount of grains within a grinding device

ABSTRACT

A method for detecting an amount of grains within a container of a rotating grinding member is described, said method comprising the steps of: supplying (FORP1) a first driving torque to the rotating grinding member during a first interval (T1) of a grinding cycle (CM); —having (CTM1OO) a first value indicative of a period of rotation of said member at the first driving torque; supplying (RP2) the rotating grinding member, during a second interval (T2) of said cycle, with a second driving torque lower than the first driving torque; —measuring (CTM50) a second value indicative of the relative period of rotation of said member at the second driving torque, processing (CDTR, CNFR) the first and second values in order to generate information (ALR) indicative of the amount of grains being within the container.

-   -   This is a continuation application of U.S. patent application        Ser. No. 12/306,303, filed Dec. 23, 2008.

The present invention relates to devices for grinding food grains or thelike, and particularly, but not limited to, devices for grinding coffeebeans.

For the purposes of the present invention, by “grain” or “bean” is meantany substantially round-shaped body or particle that can be intended forgrinding in order to be powdered. Examples of grains can be seeds,legumes, grains of wheat or coffee beans and other particles, notnecessarily food.

With particular reference to coffee grinding, a conventional coffeegrinding device, commonly known as the coffee grinder, is usuallyprovided with a container, or hopper, suitable to contain the coffeebeans to be ground and rotating grinders that provide to powder thebeans.

During grinding, as the coffee beans are decreasing within the hopper,the latter is required to be immediately filled in order to ensure thatthe coffee grinder operates at rated power, and that a good coffeebeverage will be produced. In order to facilitate this hopper-fillingoperation, it is quite useful to have an indication representative thatthe coffee beans are running out.

A known coffee machine provides using a doser that is arrangeddownstream of a conventional coffee grinder, which is suitable toreceive the ground coffee powder before the latter is used for producingcoffee beverage. This doser is typically provided with a mechanicalspring which is released, when the doser results to be filled withcoffee powder, thus sending a command signal to the coffee grinder tostop grinding. Furthermore, a control system with which this coffeemachine is provided is suitable to assess when this release has not beensensed for a preset period of time and translates this event intoinformation representative of the fact that the coffee powder can nolonger reach the top of the doser, and this allows drawing theconclusion that the coffee beans are finished within the hopper. In thiscase, the detection of the absence/presence of coffee beans is carriedout in an indirect manner, by checking the doser for the presence ofground coffee powder. This type of coffee machine has a drawback in thedoser overall size and in the extra-cost of both the doser and thedetection and control electronic system.

In order to overcome the above-cited drawback, in the so-calledsemi-automatic coffee machines, the coffee grinder is provided with asensor for detecting the current draw of the coffee grinder uponoperation. Also in this case, a control system associated with thecoffee grinder compares the value of said electric power with athreshold or reference value. Typically, a coffee grinder draws anamount of electric power proportionate to the effort made by the latterto grind the coffee, and this effort will tend to decrease as the coffeebeans to be ground decrease. Particularly, the drawn current has a lowervalue than threshold value when the effort of the coffee grinder isminimum (i.e. when the coffee beans are already finished). On thecontrary, the drawn current has a higher value than the threshold valuewhen the effort of the coffee grinder is still high because the hopperstill contains an acceptable amount of coffee beans.

This second coffee grinder is not very reliable in that the variationsin the drawn current cannot be well differentiated in order to becapable of exactly distinguishing the two conditions (absence andpresence) of coffee beans. Furthermore, the selection of the thresholdvalue for the drawn current results to be particularly problematic andimprecise in that this electric current depends, for example, on thevoltage of the network to which the coffee machine can be connected. Inaddition, it should be observed that several design parameters, interalia, the threshold value of the drawn current, which can be set uponmanufacture are subjected to, in some cases, deviations and variationsthat cannot be foreseen but which are discovered only during theoperating life of the coffee grinder. In addition, it should be observedthat these parameters can be also influenced by the ageing, mainly dueto wear and usage conditions, to which a coffee grinder is subjected andwhich typically varies with each grinding device.

A further disadvantageous aspect is also, in the instant case, theoverall size of the sensor detecting the drawn current, which isactually extra-hardware that, even though being of a small size,requires a suitable accommodation space and also entails furtherfabrication and installation costs.

An object of the present invention is to provide a method for detectingan amount of grains within a container of a grinding device.

A further object of the present invention is to provide a grindingdevice capable of detecting an amount of grains within a container ofthe grinding device.

A still further object of the present invention is to provide a computerprogram for causing a processor to carry out the method for detecting anamount of grains within a container of a grinding device.

The invention will be better understood from the detailed descriptionbelow of an embodiment thereof, which is given by way of non-limitingexample with reference to the annexed figures, in which:

FIG. 1 schematically shows a grinding device;

FIGS. 2 and 3 b show examples of waveforms representative of therotation speed of a grinding member that can be processed by means of adetection method according to an example of the present invention;

FIG. 3 a shows a diagram of the work power that can be provided to thegrinding device with the detection method according to the example ofthe invention;

FIG. 4 shows a flow chart of several steps of the detection method inaccordance with the example of the present invention;

FIGS. 5 a and 5 b show respective power diagrams that can be provided tothe grinding device according to alternative embodiments of the methodaccording to the invention, and

FIG. 6 shows a table of numerical values that can be used in a furtherexample of the method according to the invention.

An example of grinding device 1 for coffee beans, or more simply, coffeegrinder will be now described.

With reference to the diagram in FIG. 1, a coffee grinder 1 comprises anelectric motor M provided with a rotating grinding member, for example aset of grinders MC, for powdering coffee beans. Grinders MC, which areknown per se, can be conical or circular and are suitable to receive thecoffee beans to be powdered coming from a hopper (not shown in theFigure) containing the latter and typically arranged upstream of the twogrinders. Typically, the electric motor M is a DC motor that can beelectrically powered, preferably at 230 V.

It should be noted that a reduction gear MR can be advantageouslyinterposed between the motor M and the grinders MC. The reduction gearMR, which is known per se, has the function of adjusting the variationin the number of revolutions N of the grinders MC relative to that ofthe motor, upon variations in the power supplied to the motor M. Infact, being:

K the gear ratio of the reduction gear MR; ΔP the variation in the powerthat can be supplied to the electric motor; ΔN the variation in thenumber of revolutions N of the motor, the following relationshipapplies:

$\begin{matrix}{\frac{\Delta\; P}{K} = {\Delta\; N}} & (1)\end{matrix}$

The gear ratio K is a constant value greater than 1 and such that to ahigh variation in the power supplied to the motor (L1P) therecorresponds, anyway, a lower variation in the number of revolutions ofthe motor (L1N).

The coffee grinder 1 further comprises a pair of sensors SN, for exampleof known Hall-effect sensors, each being associated with one of thegrinders MC, for generating a signal, for example, an electric pulse,whenever a grinder has completed a rotation period TR about a referenceaxis of rotation. Alternatively to the pair of sensors SN, it may bealso sufficient to use an individual sensor associated with one of thegrinders, or any other known detection means (such as mechanical,optical, electronic sensors, encoders) which is suitable to generate apulse indicative that the rotation period TR of the rotating grindingelement (grinder) has been completed.

The coffee grinder 1 is further provided with an circuit board,conventional per se, comprising a processing unit UE or programmablemicro-controller, which includes, in turn, a micro-processor MIC and adata-storage memory MM and on which a management and control program forthe coffee grinder can be installed. A user interface is further mountedto the circuit board that can be controlled by the processing unit UE.The functionality and use mode of the user interface will be describedbelow.

The processing unit is operatively associated with the pair of sensorsSN, in order to receive and process the electric pulses acquiredtherefrom, and to the electric motor M, respectively, in order tocommand and control the rotation of the grinders.

For the purposes of the present invention, by “grain-absent condition”,coffee beans in the example described herein, is meant the condition inwhich insufficient or no grains are provided at the grinders MC, whenthey are brought to rotate, to achieve a satisfactory grinding.

On the other hand, by “grain-present condition” is meant the conditionin which a sufficient amount of coffee beans is provided at the movinggrinders MC, in order to achieve a sufficient grinding. Quite probably,the grain-absent condition can be attributed to the hopper beingsubstantial empty, whereas the grain-present condition derives from thefact that the hopper still contains a sufficient amount of the lattersuch as to ensure a rated power operation of the coffee grinder.

The Applicant has noted that, when the grinders are brought in rotationby the electric motor M for grinding, they adopt an angular rotationspeed ω=dζ/dt (ζ radial direction angle) which is substantiallyinversely proportional to the amount of coffee beans that isprogressively provided at the grinders. Particularly, a first value ωpgof the grinding angular speed ω substantially corresponding to thecoffee beans-present condition and a second value ωag of the grindingangular speed ω corresponding to the bean-absent condition can bedefined. During the grinding, an indication on the amount of coffeebeans provided in the coffee grinder, for example the passage from thegrain-present condition to the grain-absent condition can be representedby the variation Δω in the grinding angular speed ω that can be obtainedby the difference between the second value ωag and the first value ωpgcited above (Δω=ωag−ωpg). It appears reasonable that the first value ωpgresults lower than the second value ωag and, accordingly, the variationΔω will presumably greater than zero.

In order to operate the grinders MC, it is required to supply theelectric motor M with a driving torque corresponding to a work power PFequal to, as it is known, a percentage of the rated power PN that can bedelivered to the coffee grinder. The Applicant points out that, with thesame amount of coffee beans, as compared with the case where a firstwork power P1 is supplied to the electric motor that is for example 100%rated power, when a second work power P2 lower than P1 is supplied tothe motor, such as 50% rated power, the rotation angular speed ω isreduced, and consequently, the rotation period TR of the individualgrinder will increase.

Furthermore, the Applicant observes that when the grinders MC work atthe first power P1, they rotate with an almost constant rotation speedupon a variation in the amount of grains. In other words, when thegrinders MC work at a higher power, they are little sensitive to theamount of grains on which they operate. On the other hand, when thegrinders MC work at the second power P2, they rotate at a rotation speedwhich is more affected by the actual amount of grains on which thegrinders operate.

This different sensitiveness of the grinders MC to the presence orabsence of coffee beans is due to a different balance between the“resisting torque” (i.e. the torque exerted by the coffee beans on thegrinders) and the “driving torque or available torque” (i.e. the torquesupplied by the motor M to the grinders MC) which occurs when working atthe first power P1 or second power P2.

In fact, when the coffee grinder 1 is operated for grinding at the firstpower P1, an available torque is obtained which is so higher than theresisting torque that the grinders MC have a rotation angular speed thatis almost the same both in the presence and in the absence of coffeebeans.

When working at the second power P2, the resisting torque becomessubstantially comparable with the available torque, and thus the absenceof coffee beans causes a rotation speed of the grinders which results tobe appreciably higher than the rotation speed occurring in the presenceof coffee.

In fact, the Applicant has observed that when working at the secondpower P2, a condition occurs in which the balance is unstable andstrongly depends on the presence or absence of coffee beans at thegrinders.

The fact that the angular speed mainly depends on the presence orabsence of coffee when working at the second power P2 is,advantageously, also facilitated by the action of the reduction gear MR.In fact, the variation in the number of revolutions of the grinders ΔNis lower than the corresponding power variation ΔP=P1−P2 according tothe gear ratio K.

This allows the Applicant to conclude that the presence or absence ofcoffee can be distinguished on the basis of the grinding angular speed ωof the grinders MC in the two work conditions, i.e. at the first powerP1 and second power P2.

The detection of the grinding angular speed ω can occur in an indirectmanner, via the pair of sensors SN that are capable of generating anelectric pulse indicating that a respective rotation period TR has beencompleted by the grinders MC. Thereby, a train of electric pulses can begenerated upon grinding, such as a square wave, in which the leadingedges and trailing edges are generated by the pair of sensors SN.

With reference to FIG. 2, and particularly the waveform indicated witha), the pulse train represented herein has an amplitude equal to avoltage V and a rotation period TRa being defined by the distancebetween a first fd1 and a second fd2 trailing edge of the waveform a) orby the distance between a first fs1 and second fs2 leading edge of thesame waveform. The detection of the rotation period TRa allows having anindication representative of the grinding angular speed ω.

In FIG. 2, four test examples are shown of waveforms (a-d) generated bythe pair of sensors SN upon grinding. Particularly, the waveform a),with period TRa, relates to the case where a driving torque at the firstpower P1 is supplied to the electric motor M (which power is suitable tocarry out a satisfying grinding) and in the coffee bean-absentcondition.

The waveform b), with period TRb, relates to the case where a drivingtorque at first power P1 is supplied to the electric motor M, and in thecoffee bean-present condition.

The waveform c), with period TRc, relates to the case where a drivingtorque at second power P2 is supplied to the electric motor M (equal toa value suitable for distinguishing between the presence/absence ofgrains) and in the coffee bean-absent condition.

The waveform d), with period TRd, relates to the case where a drivingtorque at second power P2 is supplied to the electric motor M, and inthe coffee bean-present condition.

Comparing the waveform a) to the waveform b), and the waveform c) to thewaveform d), respectively, it can be observed that the differencebetween the period TRa and period TRb is much lower than the differencebetween the period TRc and the first period TRd. What has been pointedout confirms that, when a driving torque is supplied to the electricmotor M with a work power equal to 100% rated power, the variation Δω inthe rotation angular speed upon a variation in the grain amount isnearly negligible, i.e. it does not allow distinguishing between thecoffee-absent condition and coffee-present condition in an easy manner.On the contrary, when a driving torque corresponding to a substantiallyreduced power is supplied to the electric motor M, such as equal to 50%rated power, the variation Δω in the angular speed of the grindersresults so high as to allow distinguishing between the grain-present andgrain-absent conditions.

With reference to FIGS. 3 a, 3 b and 4, an example of method fordetecting an amount of grains to be used with the coffee grinder 1 willbe now described.

In FIG. 3 a a diagram is shown, which represents an exemplary course ofthe work power PF that can be provided to the motor as a function oftime, and precisely, during a grinding cycle CM. particularly, the workpower PF is expressed in terms of percentage of a rated power PNdeliverable to motor M.

By “grinding cycle” is meant the time interval in which the coffeegrinder is operated for grinding an amount of coffee beans sufficient toobtain the dose required for preparing a coffee.

With reference to FIG. 4, the example of the method according to the‘invention described herein begins with a symbolic starting step STCM.

Subsequently, during a first interval T1 of the grinding cycle CM, theprocessing unit UE provides the grinding member with a first drivingtorque CM1 (step FORP1). Particularly, the processing unit sends asuitable command to the electric motor M in order to supply the motorwith the first work power value P1 equal to, for example, 100% ofdeliverable rated power PN.

In other cases, for example depending on the type of coffee grinder, itcan be sufficient to bring the motor to a work power equal to, forexample, 90% or even 80% rated power.

With reference to FIG. 3 a, the passage from the work power PF from thezero value to the first value P1 occurs in a transient period TT1 inwhich an up-ramp takes place in order to allow the work power PF toincrease in a substantially gradual manner until when the first value P1is reached, in the example equal to 100% rated power PN deliverable tothe motor. The processing unit UE controls the electric motor M such asto keep the work power PF equal to the first value P1, preferably,throughout the first interval T1 of the grinding cycle. The Applicantobserves that, at the end of the transient period TT1 and throughout thefirst interval T1 the angular speed ω of the grinders stabilizes at analmost constant value, and thus also the rotation period TR of the same(time lapse between two electric pulses that can be generated from thepair of sensors SN) remains substantially unchanged.

With reference to the example described herein at a first portion ΔT1 ofthe first interval T1, for example at the end portion thereof, theprocessing unit UE advantageously acquires a first waveform e) (shown inFIG. 3 b) that is generated by the pair of sensors SN within the firstinterval ΔT1. Particularly, the waveform e) has: a first pair of pulseswith trailing edges delayed relative to each other by a first periodT100′; a second pair of sequential pulses with leading edges delayedrelative to each other by a second period T100″, etc. The processingunit UE acquires said periods (T100′ T100″, . . . ) that can be detectedwithin the first portion ΔT1 of the first interval T1 and proceeds tocalculate a first mean value TM100 thereof (step CTM100, for example, bymeans of arithmetic mean), based on two or more measured periods. Thefirst mean value TM100 results indicative of a respective first periodof rotation of the grinders when the coffee grinder is supplied with thefirst driving torque CM1.

Subsequently, during a second interval T2 of the grinding cycle CM, theprocessing unit UE supplies the grinders with a second driving torqueCM2 lower than the first driving torque CM1 (step RP2). In order toobtain the variation in the driving torque, the processing unit UEcommands the reduction in the work power PF supplied to the electricmotor M from the first work power value P1 to the second work powervalue P2 being substantially preferably equal to 50% rated power. Itshould be noted that said second work power value P2 can also be, forexample, equal to 60% or 70% rated power or other values suitable to thepurpose.

As shown in the diagram in FIG. 3 a, the reduction in the work power PFcauses a second transient period TT2 that is due, also in this case, toa down-ramp required for passing from the first P1 to second P2 workpower value. The processing unit DE thus holds the work power PF equalto the second value P2 throughout a second interval T2 and, preferably,until the end of the grinding cycle CM. The second interval T2 resultsto be much lower than the first interval T1. The Applicant points outthat this advantageously allows having a coffee grinder operating atrated power (first power value P1 first driving torque CM1) almost forthe entire (first interval T1) grinding cycle CM and operation atreduced power (second value P2-second driving torque CM2) for a muchshorter interval relative to the grinding cycle (second interval T2).Numerical examples of possible durations of the intervals T1 and T2 andgrinding cycle CM will be set forth below.

During a second portion ΔT2 of the second interval T2, the processingunit DE acquires a second waveform f) (shown in FIG. 3 b) generated bythe pair of sensors SN. It should be noted that, in the exampledescribed above, the second portion ΔT2 substantially corresponds to the5 second period T2. In greater detail, the waveform f) has, for example,a respective first pair of sequential pulses with trailing edges delayedrelative to each other by a respective first period T50′, a respectivesecond pair of sequential pulses with leading edges delayed relative toeach other by a respective second period T50″, etc. What has been statedfor the first two pairs of sequential pulses can be expressed for allother pairs of pulses forming the waveform f). Even in this case, theprocessing unit DE proceeds to calculate a second mean value TM50 (stepCTM50) obtained, for example, by the arithmetic mean of two or moreperiods detectable within the second portion ΔT2 of the second intervalT2. The processing unit thus measures the second mean value TM50indicative of a respective second period of rotation of the grinderswhen the second driving torque CM2 is supplied to the coffee grinder.

At this stage, the processing unit UE starts to process the first TMI00and second TM50 mean values to generate information indicative of theamount of grains within the container.

For example, the processing unit DE implements the formula below (stepCDTR):

$\begin{matrix}{{\Delta\;{TR}} = {\frac{\left( {{{TM}\; 50} - {{TM}\; 100}} \right)}{{TM}\; 50} \cdot 100}} & (2)\end{matrix}$As may be seen in the relationship (2), the processing unit startsassessing the difference between the first TMI00 and second TM50 values(numerator) in order to generate a quantity ΔTR representative of adeviation of the period of rotation in the work condition at the firstpower P1 relative to the work condition at the second power P2.Particularly, the quantity ΔTR is a percentage variation relating to thesecond mean value TM50 (denominator) of the mean period betweensequential pulses generated by the pair of sensors SN when the coffeegrinder is supplied with the first driving torque CM1 and subsequentlythe second driving torque CM2.

The processing unit DE then starts comparing (step CNFR) the quantityΔTR with a predetermined threshold value ΔTS stored in the memory MM.Particularly, the threshold value ΔTS is suitable to distinguish thecoffee bean-present condition from the coffee bean-absent condition.

Particularly, the Applicant states that the threshold value ΔTS is setupon design of the coffee grinder, and more particularly, selectedwithin an interval of values ranging between a duly calculated upperlimit value ΔTP and lower limit value ΔTA.

For example, the upper limit value ΔTP is calculated by the processingunit UE by applying the (2) in the coffee bean-present condition:

$\begin{matrix}{{\Delta\;{TP}} = {\frac{\left( {{{TP}\; 50} - {{TP}\; 100}} \right)}{{TP}\; 50} \cdot 100}} & (3)\end{matrix}$

The value TAIOO is the mean value of the period between two sequentialpulses generated by the pair of sensors SN when the, first work power PIis supplied to the motor. The value TPIOO is calculated based toelectric pulses detected in the first portion ˜T1 of the first intervalT1 of the grinding cycle CM.

The value TP50 is the mean value of the period between two sequentialpulses generated by the pair of sensors SN when the motor is suppliedwith the second work power P2. The value TP50 is calculated based onpulses detected by the sensors in the second portion ΔT2 of the secondinterval T2 of the grinding cycle CM.

The lower limit value ΔTA is obtained by applying the (2) in the coffeebean-absent condition:

$\begin{matrix}{{\Delta\;{TA}} = {\frac{\left( {{{TA}\; 50} - {T\; A\; 100}} \right)}{{TA}\; 50} \cdot 100}} & (4)\end{matrix}$

The value TPIOO is the mean value of the period between two sequentialpulses generated by the pair of sensors SN when the first work power issupplied to the motor P1. Also in this case, the calculation of TA100 iscarried out based on pulses generated during the first portion ΔT1 ofthe first interval T1 of the grinding cycle CM.

The value TA50 is, instead, the mean value of the period between twosequential pulses generated by the pair of sensors SN when the motor isprovided with the second work power P2. The value TA100 is calculatedbased on pulses detected in the second portion ΔT2 of the secondinterval T2 of the grinding cycle CM.

As stated above, the threshold value is suitably selected such as tocomply with the following condition:

ΔTA<ΔTS<ΔTP.

When the quantity ΔTR is lower than the threshold value ΔTS, the coffeegrinder is in the substantial coffee bean-absent condition (option N inthe chart in FIG. 4). In this case, the processing unit UE signals (stepALR) the state of substantial coffee bean-absent state via a userinterface provided on the coffee grinder. Particularly, the processingunit UE activates, via said interface, a signalling device for the user,such as a display being operatively associated with said interface onwhich a warning message appears, like “NO COFFEE”. Alternatively to orin combination with the display, other suitable signalling devices forthe user are a light alarm, for example a red Led that lights up whenthere is no coffee, or a sound alarm, for example a buzzer, capable ofemitting a sound when there are no coffee beans.

In the case where the quantity ΔTR is higher than the threshold valueΔTS, the coffee grinder is in the coffee bean-present condition (optionY in the diagram in FIG. 4) and the processing unit UE does not provideto send any alarm signal.

It should be noted that at the end of the second interval T2 thegrinding cycle CM can be considered finished and the processing unit UEstops the supply of work power PF to the electric motor M graduallypassing from the second work power value P2 to a substantially zerovalue (step EDCM).

As relates to the duration of the time intervals described above,typically, the grinding cycle CM has a duration of 8-10 secondscorresponding to about a number of pulses ranging between 90 and 120.The second interval T2 preferably has a duration of several milliseconds(about 7-8 pulses). Particularly, the rather reduced duration of thesecond interval (a few milliseconds) relative to the first interval T1(slightly less than 8-10 seconds) allows the coffee grinder to work,during the grinding cycle CM, at a substantially reduced power only fora short time, which advantageously does not affect the quality ofgrinding and the obtainment of a good coffee beverage.

Furthermore, in the example described herein, the second interval T2 isarranged after the first interval T1 and corresponds to an end intervalof the grinding cycle CM. This situation is preferred, in that,considering that a reduction in the work power supplied to the coffeegrinder can result irritating to hear, it allows to disguise the workpower decrease required for carrying out the method of the inventionlike the normal power decrease occurring at the end of the grindingcycle to turn off the coffee grinder.

Furthermore, in alternative embodiments of the method according to theinvention, the second interval T2 can also not be necessarily sequentialto the first interval T1, or during a grinding cycle, more intervals(similar to the first interval T1) may occur in which the coffee grinderis brought to the first power value PI and also more intervals (similarto the second interval T2) may occur in which the coffee grinder isbrought to work at the second work power value P2.

With reference to FIG. 5 a, in a further example of the method accordingto the invention, the second driving torque CM2 can be supplied to thegrinding member by applying the second power value P2 for the respectiveintervals T2′ and T2″ that are arranged at the ends of the grindingcycle CM, respectively, and separated from each other by the firstinterval T1 during which the grinding member is supplied with the firstdriving torque CM1, corresponding to the first power value P1.

The division of the grinding cycle into these time intervals allowsproceeding to the detection of the amount of coffee beans at differentpoints of the grinding cycle, such as at the beginning and at the end ofthe latter. Particularly, the processing unit UE carries out once againthe process steps described above with reference to the flow chart inFIG. 4. In this example, in the relationship (2) appears the second meanvalue TMSO calculated on the basis of pulses generated by the pair ofsensors within a third portion ΔT3, substantially corresponding to theinterval T2′, when the second driving torque is applied to the motorCM2. Furthermore, in (2), the first mean value TM100 is used, which iscalculated on the basis of pulses generated by the sensors in a fourthportion ΔT4 substantially placed at the beginning of the first intervalT1 of the grinding cycle. Thereby, it is possible to have an indicationrepresentative of the amount of coffee beans at the very beginning ofthe grinding cycle.

In this example, the processing unit carries out once again the methodaccording to the invention (FIG. 4) even at the end of the grindingcycle. particularly, in (2) appears a first mean value TMIOO calculatedwith reference to a fifth portion ΔT5 of the first interval T1, which issubstantially placed at the end of the latter and corresponding to thecondition of first driving torque CMI supplied to the coffee grinder.Furthermore, in (2) appears a second mean value TM50 calculated withreference to a sixth portion ΔT6 corresponding to the interval T2″placed at the end of the grinding cycle. The processing unit UE is thuscapable of generating information representative of the amount of grainsalso at the end of the grinding cycle.

This embodiment of the method according to the invention, combining thedetection at the beginning and at the end of the grinding cycle, allowsadvantageously increasing the possibility of detecting the amount ofcoffee in the most correct manner possible, and signalling even moreimmediately when the latter is finished.

In FIG. 5 b is shown another example of the method according to theinvention.

The grinding member, during a grinding cycle CM is first brought to thefirst power value P1 (100% rated power) to supply the first drivingtorque CM1 for a respective first interval T1′. Subsequently, for arespective second interval T2′, the grinding member is supplied with thesecond driving torque CM2 (second power value P2-50% rated power) andthen, for a further first interval T1″ the motor is brought back to thefirst power value P1. The grinding cycle ends with a further secondinterval T2″ in which the grinding member is supplied once again withthe second driving torque CM2 corresponding to the second work powervalue P2.

What has been stated in the above example of method (FIG. 5 a) can bealso repeated with the division of the grinding cycle as shown above(FIG. 5 b). In this case, the (2) is implemented, for the first time,with first and second mean values calculated with reference to the thirdportion ΔT3, situated in a final portion of the respective firstinterval T1′, and the fourth portion ΔT4 situated at the respectivesecond interval T2′. The processing unit thus implements the (2) for thesecond time with first and second mean values calculated with referenceto the fifth portion ΔTS situated at the end of the further firstinterval T1″ and to the sixth portion ΔT6 situated at the further secondinterval T2″.

Also this embodiment of the method according to the inventionadvantageously allows increasing the possibility of detecting the amountof coffee in the most correct and precise manner possible, andoutputting a signal when the latter is finished.

Generally, the selection of the number and frequency of intervals of thegrinding cycle at which the second torque is to be supplied to thegrinding member depend on the whole duration of the grinding cycle andon the desired precision of detection.

In a further alternative embodiment of the invention, the detectionmethod according to the invention can provide that the first valueTM100, indicative of the period of rotation of the grinding member atthe first driving torque CM1 and not particularly sensitive to thepresence/absence of coffee, is not detected during the grinding cycle CMby is defined upon design of the coffee grinder and stored in the memoryMM associated with the processing unit UE. On this account, the methodaccording to the invention can be said to comprise a step of planing afirst mean value TM100 indicative of the period of rotation of thegrinding member at the first driving torque.

The preferred relationship (2) in the examples of the method accordingto the invention that have been considered herein above can also bereplaced with other mathematic formulae that carry out another type ofnormalization, or that, for example do not obtain values expressed as apercentage.

In a further alternative embodiment, considering the quantities alreadyused in (2), the following relationships applies as an alternative torelationship (2):

$\begin{matrix}{{\Delta\;{TR}} = {\frac{\left( {{{TM}\; 50} - {{TM}\; 100}} \right)}{{TM}\; 50} \cdot 100}} & (5)\end{matrix}$

As may be seen, relative to (2), in the relationship (5) the difference,at the numerator, between the second TM50 and the first TM100 meanvalues indicative of the period of rotation is related, at thedenominator, to the first mean value TM100 and not the second mean valueTM50. Practically, in (5), the percent variation is referred to thefirst mean value TM100.

In another embodiment, in place of (2) or (3), considering the samequantities as in (2), the following can be also written:

$\begin{matrix}{{\Delta\;{TR}} = {\frac{\left( {{{TM}\; 50} - {{TM}\; 100}} \right)}{{TM}\; 50} \cdot K^{\prime}}} & (6)\end{matrix}$

In this case, the difference between the first TMSO and second TM100mean values, reported at the denominator to the second mean value TMSO,is multiplied by a constant K′ (for example of value 1, 10, 50 or 1000or other value determinable by those skilled in the art upon designbased on the mechanical characteristics of the apparatus). Relative to(2) or (5), the quantity ΔTR is not, accordingly, a percentagevariation.

The selection of a mathematic relationship over another between (2), (5)and (6) depends, for example, on the calculation power of themicroprocessor mounted to the circuit board and on the specific designtolerances of the grinding device.

The example of detection method described herein can be also usedoutside the field of coffee grinders, i.e. it can be used in anygrinding device for grains or beans of food or the like.

As relates to the definition of the preset threshold value ΔTS, theApplicant notes that it is possible to define a dynamic threshold valueATSD, i.e. capable of varying during the operating life of the coffeegrinder, which is calculated, for example, based on the number ofgrinding cycles that have been carried out. In greater detail, upon thedesign of the coffee grinder, it is possible to define, in the modedescribed above for the threshold value ΔTS, more threshold values, eachof which to be attributed to a range of values corresponding to thegrinding cycles that have been carried out by the coffee grinder.

With reference to FIG. 6, the table reported herein has a first columnshowing the number of grinding cycles NCM of the coffee grinder and asecond column showing the respective dynamic threshold value ΔTSD. Inthe first line of the table, a first range of values of grinding cycles(for example, 0-1000) is associated with a respective dynamic thresholdvalue (for example, ΔTSD1). In the second line of the table, theassociation is shown between a second range of values of grinding cycles(for example, 1001-3000) and a second dynamic threshold value (forexample, ΔTSD2) and the like, for all the other lines in the table. Thetable in FIG. 6 is thus built upon design of the coffee grinder inconsideration of the wear and ageing of the latter. During the operatinglife of a coffee grinder, the threshold value ΔTS is subjected tovariations that can make non-optimum the detection method, which isbased on the use of an individual threshold value.

It should be noted that, in order to implement this variant embodimentof the method according to the invention, said table requires to bestored in the memory MM and the processing unit to be provided with acounter of the grinding cycles of coffee grinder.

From the point of view of the method according to the invention, theprocessing unit, after the percent quantity ΔTR has been calculated(step CDTR), acquires from the counter the number of grinding cycles NMCthat have been carried out by the coffee grinder and starts querying thetable until when the corresponding dynamic threshold value ΔTSD isdetermined.

The use of the table in FIG. 6 by the processing unit UE advantageouslyallows to have a more precise detection of the amount of grains, andcapable of dynamically taking into account the normal performancevariations to which the coffee grinder is subjected due to ageing.

As may be seen, the object of the invention is fully achieved, in thatthe example of detection method described herein allows obtaining aprecise assessment of the absence or presence of grains to be ground andcan avoid providing the addition of new hardware, but merely the suitable programming of circuit cards with which a conventional grindingdevice is already provided.

For example, it should be observed that the pair of Hall-effect sensorsare usually already used for detecting the period of rotation of thegrinding member as information representative of the amount and finenessof the ground coffee.

Furthermore, the above-cited counters are already comprises within themicroprocessor, which, as it is known, is provided with so-called timersand conventional integrated counters.

It should be further noted that, for example, the method describedherein implements rather a simple mathematic relationship (2), (5) or(6), and in which the processing times with a conventionalmicroprocessor are minimum relative to the duration of a grinding cycle.Also the subsequent steps of comparison and querying of table in FIG. 6can be economically implemented by a standard microprocessor.

Finally, the detection method according to the invention is not based onthe analysis and detection of inherent electric quantities of the coffeegrinder, such as for example the current draw, but on quantities, suchas percent variations, related to the rotation of the grinding memberand mostly depending on the present amount of coffee in the coffeegrinder, and not on the type of coffee grinder. In greater detail, theuse of a mathematic relationship of the type (2), (5) or (6) thatestablishes a relation between detected quantities (TM50 and TM100)makes the method according to the invention substantially independent onthe type and physical configuration (motor, grinding member, powersupply voltage) of the coffee grinder.

1. A grinding device comprising: a rotating grinding member; an electricmotor operatively associated with said rotating grinding member andsuitable to move said rotating grinding member; and a container arrangedupstream of said rotating grinding member for containing grains to bepowdered during a grinding cycle, characterized in that said electricmotor is controllable to supply the rotating grinding member with atleast two different driving torque values, and said grinding devicefurther comprises: a detector for detecting a period of rotation of therotating grinding member, said detector being operatively associatedwith said rotating grinding member; and a processing and command unitconnected to the detector and the electric motor, wherein the processingand command unit: controls the electric motor to supply the rotatinggrinding member with a first driving torque value during a firstinterval of a grinding cycle; uses the detector to detect a first valueindicative of a period of rotation of said rotating grinding memberbeing driven by the first driving torque value; controls the electricmotor to supply the rotating grinding member, during a second intervalof said grinding cycle, with a second driving torque value, said seconddriving torque value being less than the first driving torque value;uses the detector to detect a second value indicative of a period ofrotation of said rotating grinding member being driven by said seconddriving torque; and processes the first value and the second value togenerate information indicative of an amount of the grains within thecontainer.